This book explains how Abraham Lincoln-the greatest flip-flopper in our nation's history-moved from explicitly defending slavery in the South to issuing what's been called "a poor document, but a mighty act," the Emancipation Proclamation.

Even before the Lincoln-Douglas debates, all of Abraham Lincoln's public statements reflected his belief that the Constitution protected slavery. He held that it was legal in the southern states where it already existed and that as President he was bound to protect it. He would act against this only in the case of "indispensable necessity." Eventually, that indispensable necessity arrived.

Not just words, but Lincoln's actions confirmed his commitment not to interfere with slavery. Once the war began, he did not allow attempts by generals in the field to emancipate the slaves in occupied territory. To appease the South, he proposed an amendment to the Constitution that would allow slavery to continue where it already existed. The South did not yield and the war continued. He proposed a plan to compensate slaveholders and relocate former slaves outside the United States. The South did not yield and the war continued.

Lincoln believed the South acted contrary to the Constitution by seceding from the Union and proclaiming themselves a foreign nation. While Lincoln did not recognize secession as legal, the Confederacy was regarded as they would be under international law; flags of truce were honored, and prisoner exchanges were negotiated. Therefore, by complying with their desire to be treated as a separate nation, international law allowed Lincoln to do what the Constitution barred him from doing in time of peace. This enabled him to advance the Emancipation Proclamation as a legitimate war strategy he hoped would unite the country, break the Confederate will, and return it to a new and stronger Union of United States.

It was September 1862 when the "indispensable necessity" of emancipation arrived. When asked where the Constitution gave the President this power, Lincoln asserted that the Constitution invested the President "with the law of war in time of war." Morality justified it, but it was the law of war that legalized Lincoln's "mighty act."

Fast forward to September 2001. Per the author, all presidents since Lincoln's time have, to great controversy, cited the international law of war as a measure and source of their powers as commander-in-chief. He also notes the irony that the same legal theory invoked to free the slaves in 1862 today is used to detain Iraqi war prisoners. Lincoln's was a mighty act, and the author's contribution to our understanding of its importance to history and humanity make this a mighty book.

Burrus M. Carnahan is a professional lecturer at George Washington University and holds a JD from Northwestern University; LL M University of Michigan; previously a former Judge Advocate, US Air Force specializing in international law; and currently is Foreign Affairs Officer, Office of Nuclear Energy, Safety and Security, U.S. Department of State. He is past president of the Lincoln Group of the District of Columbia, and is the author of numerous journal articles on international law, the law of war, and arms control.